1. Field of the Invention
The present invention relates to a semiconductor memory device and methods for manufacturing and driving the same. More particularly, the present invention is directed to a magnetic random access memory (MRAM) and methods for manufacturing and driving the same.
2. Description of the Related Art
MRAM, which is one type of next-generation memory device, has properties of both DRAM and SRAM, and also has nonvolatile characteristics of a flash memory.
The conventional MRAM includes a MOS transistor and a magnetic tunneling junction (MTJ) layer, which are coupled to each other. Data is stored in the MTJ layer of the MRAM. In the conventional MRAM, a tunneling current that passes through the MTJ layer also passes through the MOS transistor. Therefore, a resistance of the MOS transistor restricts the selection of the MTJ layer. Accordingly, when the magnetic resistance (MR) ratio of the MTJ layer is kept low, the data recorded in the MTJ layer cannot be read out precisely, thereby limiting the effective use of a conventional MRAM.